Currently in print:
Titan Books can be bought at Amazon or your local bookstore, also directly from Titan.
Comics Revue can be ordered at Rick Norwood´s site, also Rick´s trade paperbacks ´Lady in the Dark´, `Dark Angels´and ´Live Bait´.
Ken Pierce Books basically carries all of the above (including some back issues of Comics Revue), but you can´t subscribe to Comics Revue there.
Out of print books can usually be found (at a price) via eBay. Old issues of Comics Revue might be very difficult to get hold of ...